From the view of polymerization models, it is true that it is just the amount of porogen different between bulk and precipitation polymerization. However, the materials obtained by bulk polymerization generally show better MIP effect than that of precipitation polymerization. While precipitation polymerization generally afford materials with uniform shape (such as microbeads).  

Through poregen the spherical edge polymerization takes place.  Normally alkyl trialkoxy or trichloro silane are used as porogen.  This is not only act as porogen, but also increase the rate of polymerization.

　　From the view of polymerization models, it is true that it is just the amount of porogen different between bulk and precipitation polymerization. However, the materials obtained by bulk polymerization generally show better MIP effect than that of precipitation polymerization. While precipitation polymerization generally afford materials with uniform shape (such as microbeads).  

In bulk polymerization you don't use solvent, in precipitation polymerization you do, and also stabilizers.

thanks for your opinion